1. Technical Field
The present invention relates to a system, such as a touch screen system, using light for determining properties of an object placed on a surface.
The present invention also relates to an apparatus, object and a method for use in such a system.
2. Description of Related Art
With current infrared touch screens it is not possible to detect more than one position at a time, because they use a method that scans a grid built up by LEDs and light sensors. A position is selected in the grid by interrupting a light beam in horizontal and vertical direction. The detection of multiple points is not possible for all positions, because the selection of one point can block the correct detection of other points. Therefore, this technique is less usable for multi point detection. Furthermore, shapes cannot be detected with the current technique; only some form of ‘bounding’ box can in principle be detected in the grid of LEDs and sensors.
In order to overcome these problems the co-pending provisional application with U.S. Ser. No. 60/660,366 filed on 10 Mar. 2005 for Sander B. F. van de Wijdeven and Tatiana A. Lashina for SYSTEM AND METHOD FOR DETECTING THE LOCATION, SIZE AND SHAPE OF MULTIPLE OBJECTS THAT INTERACT WITH A TOUCH SCREEN DISPLAY, which had not been published at the time of filing of the present application, proposes a system with on the border of the screen a number of light emitters (e.g. infrared LEDs) and a number of light sensors. The lights of the screen are initially turned off and then the lights are turned on one by one. The light (lamp or LED) shines a beam of light, which is detected by the sensors on opposite sides of the screen. When there is an object in between the light and the opposite side of the screen this object casts a shadow. This shadow is detected by the sensors by the absence of light. The combination of knowledge about what light is turned on and what sensors detect or do not detect the light (compared to the calibration state) allows the calculation of an area in which the object must be. If a complete cycle is made in which all the light emitters are turned on, the position, shape and size of the object may be determined.